"""You are given a 0-indexed integer array tasks, where tasks[i] represents the difficulty level of a task. In each round, you can complete either 2 or 3 tasks of the same difficulty level.

Return the minimum rounds required to complete all the tasks, or -1 if it is not possible to complete all the tasks.

 

Example 1:

Input: tasks = [2,2,3,3,2,4,4,4,4,4]
Output: 4
Explanation: To complete all the tasks, a possible plan is:
- In the first round, you complete 3 tasks of difficulty level 2. 
- In the second round, you complete 2 tasks of difficulty level 3. 
- In the third round, you complete 3 tasks of difficulty level 4. 
- In the fourth round, you complete 2 tasks of difficulty level 4.  
It can be shown that all the tasks cannot be completed in fewer than 4 rounds, so the answer is 4.
Example 2:

Input: tasks = [2,3,3]
Output: -1
Explanation: There is only 1 task of difficulty level 2, but in each round, you can only complete either 2 or 3 tasks of the same difficulty level. Hence, you cannot complete all the tasks, and the answer is -1.
 

Constraints:

1 <= tasks.length <= 105
1 <= tasks[i] <= 109
 

Note: This question is the same as 2870: Minimum Number of Operations to Make Array Empty."""

class Solution {
public:
    int minimumRounds(vector<int>& tasks) {
        std::unordered_map<int, int> freq;
        for (int i = 0; i < tasks.size(); i++) {
            freq[tasks[i]]++;
        }
        int count = 0;
        for(auto it = freq.begin(); it != freq.end(); it++) {
            count++;
            if (it->second < 2) { return -1;}
            if (it->second > 3) {
                int m = it->second / 3;
                int n = it->second % 3;
                if (n == 0) count += m-1;
                else count += m;
            }
        }
        return count;
    }
};